Method and apparatus for manufacturing waterproof footwear with attached compressible lining

ABSTRACT

A method and apparatus for making a lined waterproof footwear product, and footwear product formed therefrom, are provided. A last, having an exterior surface configured to correspond to the size and shape of the interior surface of the footwear product, is covered with a microcellular lining material. An injection mold comprises shells having a pre-determined configuration to mold an upper portion that attaches to the lining during the molding process. In the finished footwear product, the molded upper portion has a molded foot portion that extends around the wearer&#39;s foot and an upwardly-extending molded portion that covers a part of the lining while leaving another part of the lining uncovered.

FIELD OF THE INVENTION

The invention is in the field of footwear and, in particular, pertainsto an improved method and apparatus for making waterproof footwear withlining, such as an insulation-type lining in the case of winterfootwear, and waterproof footwear formed thereby.

BACKGROUND

Different manufacturing methods are known for making lined (e.g.insulated) waterproof footwear (e.g. winter boots). These include theconventional lasted process, a process for injection molding the mainboot and then inserting into it a loose insulating liner, and, forrubber boots, a vulcanization process applied to a lining layer. Each ofthese known methods involves numerous separate steps which increasescosts and impedes efficiency.

The lasted process is an old, well-known method which uses a last havingthe shape of the intended boot, the last being a three dimensional modelfor the intended boot. By this method, the boot materials are formed andfitted onto the last. Hiking boots are typically made in this manner.The selected materials, which may be leather and/or fabrics, includingmaterial for a lining layer, are cut into pieces using the last as amodel, assembled with a waterproof membrane layer, for example aGore-Tex membrane, sewn together and then cemented to a rubber sole.

The vulcanization process is also a well-known method for making rubberboots and uses a last. By this method, a lining material is formed tofit over a last and positioned to cover the last. Unvulcanized (i.e.raw) rubber is cut into pieces according to a pattern and the pieces arelaid over and cemented to the lining material covering the last. Afterthe positioning of the pieces has been completed, the assembly is putinto a heated oven and subjected to heavy pressure which causes the rawrubber to vulcanize and adhere to the insulating microcellular lining.

These known methods involve many separate steps or entail multiplesub-processes which increase production costs. Therefore, a simplermethod would constitute a desirable improvement.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a method formaking a lined waterproof footwear product. A last has an exteriorsurface configured to correspond to the size and shape of the interiorsurface of the footwear product. At least a portion of the exteriorsurface of the last is covered with a microcellular lining material. Afirst mold is provided for injection molding the footwear productwhereby the first mold comprises first and second plates, and first andsecond shells wherein each shell has a pre-determined configuration tocooperate with the exterior surface of the lining covered last to form:(i) a pre-injection cavity between the shells and the lining coveredlast when the lining covered last is located between the first andsecond shells, and between the first and second plates located onopposite sides of the shells, and the plates are closed in position forinjection molding; and, (ii) an injection cavity, defining theconfiguration of the footwear product, between the shells and the liningcovered last when the plates have been tightly closed, the liningcovered last is between the closed plates and injection material isbeing injected into the injection cavity whereby the injection pressurecauses the microcellular lining material to compress and therebyreconfigure from the pre-injection cavity to the injection cavity. Thelining covered last is located between the first and second shells, andbetween the first and second plates located on opposite sides of theshells. The plates are closed in position for injection molding, therebyforming the pre-injection cavity between the shells and the liningcovered last. An injection material is injected under pressure into thepre-injection cavity whereby the pre-injection cavity is reconfigured tothe injection cavity, and injecting the injection material until theinjection cavity is filled with the injection material. The injectionmaterial is hardened in the injection cavity whereby the hardenedinjection material attaches to the microcellular lining material andforms the footwear product over the last. The first mold is opened toseparate the plates and shells and expose the finished footwear productand removing the footwear product from the last.

The injection material may be a thermoplastic material which is heatedprior to the injecting step, is molten when injected, and is hardened bycooling. Preferably, the last is comprised of a hard, durable materialselected from a group consisting of hardened aluminum, steel andstainless steel. The covering of the last may comprise positioning asock lining over the last.

The footwear product may be an upper part of another footwear product,with a sole made by injection molding by a second mold comprising firstand second sole plates and first and second sole shells. The sole formedin a sole cavity between the first and second sole shells by injectinginjection material into the sole cavity, and attached to the upper toform the other footwear product. The sole may be attached to the upperby injection material during the injection molding and cooling of theupper. A second sole may be injection molded concurrently with theinjection molding of the upper. Preferably, an injection port is locatedon the outside of the first mold.

The invention further provides apparatus for making a lined waterprooffootwear product, wherein a last has an exterior surface configured tocorrespond to the size and shape of the interior surface of the footwearproduct. A first mold is provided for injection molding the footwearproduct whereby the first mold comprises first and second plates, andfirst and second shells wherein each shell has a pre-determinedconfiguration to cooperate with an exterior surface of a lining coveredlast to form: (i) a pre-injection cavity between the shells and thelining covered last when the lining covered last is located between thefirst and second shells, and between the first and second plates locatedon opposite sides of the shells, and the plates are closed in positionfor injection molding; and, (ii) an injection cavity between the shellsand the lining covered last when the plates have been tightly closed,the lining covered last is between the closed plates and injectionmaterial is being injected into the injection cavity whereby theinjection pressure causes the microcellular lining material to compressand thereby reconfigure from the pre-injection cavity to the injectioncavity; whereby the lining covered last comprises the last with at leasta portion of the exterior surface of the last covered with amicrocellular lining material and, the configuration of the injectioncavity defines the configuration of the footwear product.

Using the apparatus, the footwear product is formed by injecting underpressure into the pre-injection cavity an injection material therebycausing the pre-injection cavity to reconfigure to the injection cavity,until the injection cavity is filled with the injection material, andhardening the injection material in the injection cavity. The footwearproduct may be an upper part of another footwear product, with theapparatus further providing a second mold, comprising first and secondsole plates and first and second sole shells for injection molding asole for attachment to the upper. Preferably, an injection port islocated on the outside of the first mold.

The invention further provides a footwear product or upper and otherfootwear product made by the foregoing steps.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail below with reference to thefollowing drawings.

FIG. 1 is a perspective view illustrating a layer of lining materialpositioned over and covering a last in accordance with the invention.

FIG. 2 is a sectional plan view of an injection molding machine inaccordance with the invention for making a lined, waterproof boot,having an upper mold and two sole molds for cyclically injecting, ineach cycle, both a boot upper and a sole and attaching a previouslymolded sole to the boot upper that is molded during the cycle. A lastcovered with a sock lining is shown in position between two boot uppermold plates and shells, ready to close the plates around the last andcover the end of the plates with a sole plate containing a previouslyinjection-molded sole. Also shown is a second sole plate that is coupledto the sole plate covering the boot upper mold by a rotatable plate,whereby the second sole plate is closed onto a cover plate when theupper mold is closed and injected with injection material to form a soleduring the same injection cycle of injection-molding the boot upper.

FIG. 3 is a perspective view of a waterproof boot having an interiorattached lining made in accordance with the invention.

DETAILED DESCRIPTION

The subject invention provides an improved method and apparatus formaking lined waterproof footwear, and waterproof footwear formedthereby. The method uses an injection molding process and a last. Apredetermined thermoplastic material is selected as appropriate for theapplication and used as the injection material. As illustrated by FIGS.1 and 2, a last 10 is advantageously used within the injection mold 55for the upper of the footwear product to position and attach to theupper 130 a lining 20. The upper mold 55 comprises two shells 70 and twoplates 60. The shells 70 are designed to complement both theconfiguration of the layer of lining 20 and the dynamic changes thelining configuration undergoes from the pressure applied to it duringthe course of the injection process so as to create a cavity 80 having apredetermined configuration of the upper 130 of the footwear product(see FIG. 3) to be made by the mold.

The thermoplastic material, in a fluid state, is injected over the last10 covered with a lining material (also referred to herein as a socklining) 20 while the last 10 is located within the upper mold 55 andallowed to set (i.e. harden) within the mold to form a lined waterprooffootwear product 120 as illustrated by FIG. 3. While in its fluid stateafter being injected into the upper mold 55, the thermoplastic materialcovers the sock lining 20 and attaches to the sock lining 20 as it sets.For the exemplary, illustrated embodiment a winter boot is provided;however, it is to be understood that the invention is not limited to anyparticular type of boot and also provides other types of linedwaterproof footwear including rain boots and shoes.

As illustrated by FIG. 1, the last 10 functions as a three dimensionalmodel or pattern which is used to size and fit the sock lining 20. Thelast 10 is made of a hard metal, usually of hardened aluminum or steelfor high durability. The exterior surface of the last 10 is configuredto mirror (i.e. correspond to) the size and shape of the interiorsurface of the item of footwear that is to be made by the upper mold 55.A predetermined relatively thick, microcellular lining material issized, cut and sewn to match the size, shape and configuration of theexterior surface of the last 10 and fit tightly over the last 10 to formthe sock lining 20. The sock lining 20 may, for example, be chosen toprovide insulation to a winter boot such as that shown by FIG. 3. Whenthe lining pieces have been sewn together 30, the resulting sock lining20 is positioned over the last 10 to cover it as shown in FIGS. 1 and 2.

By “microcellular” it is meant that the material is comprised of a largenumber of cells and having a compression—expansion property so that thelining material is caused to compress during the process of injectingthe injection material into the mold cavity, under pressure, and thenexpand after the molded boot has been removed from the mold and takenoff the last.

In the example of the illustrated embodiment a neoprene microcellularmaterial manufactured by Nam Liong Enterprises Co. Ltd. of Tainan,Taiwan, grade WS-2H comprising 30% polychloroprene rubber and 70%styrene butadiene rubber, is selected for use for the lining material.This is a foamed synthetic rubber product (i.e. containing gas cells)and is selected for the illustrated application of a winter boot becauseof its relatively good insulation characteristic. Examples of othersuitable microcellular materials are foam blends such as polyurethane orEVA (ethylene vinyl acetate)—based blends. For the illustrated example,the selected lining material has a relatively large thickness of 3 mmbut it will be understood by the skilled reader that the thickness to bechosen will vary from application to application according to designchoices for the particular footwear product to be formed and theparticular mold materials to be used.

To mold the boot upper 130, the last 10 with sock lining 20 is attachedto the upper mold 55 using the last holder 40 whereby it is positionedin the cavity 80 between the two sets of plates 60 and shells 70 of theupper mold 55 as illustrated by FIG. 2. The plates 60 and shells 70 arecomprised of a hard metal such has hardened aluminum or steel for highdurability. The shells 70 are precision measured to take intoconsideration the thickness of the sock lining 20 when it is compressedduring the injection molding process. A key criteria for the design ofthe upper mold 55 is to provide a cavity 80, referred to as thepre-injection cavity, between the interior surfaces of the mold 55 andthe sock lining 20 having a configuration which accounts for anon-uniform compression of the sock lining 20 when it is, subsequently,subjected to pressure from an injection of thermoplastic material intothe cavity 80. This is because it is the final configuration of thecavity, referred to as the injection cavity, after the injection of thethermoplastic material with its attendant pressure applied to the socklining 20, that becomes occupied by thermoplastic material and definesthe configuration of the footwear product made by the process.Therefore, the upper mold 55, the sock lining 20 and the cavity 80together must be designed to account for a non-uniform compressionfactor of the sock lining 20 over the area of the sock lining 20. Thus,the combination of the last 10 with sock lining 20 in position with themold shells 70 and plates 60 closed there over, together operate in anovel manner to form the cavity that is required to make the intendeditem of footwear in like manner to a conventional mold core having nolining material.

For the injection process, the plates 60, 105 of the upper and solemolds 55, 115 are tightly closed and sealed whereby the last 10 withsock lining 20 is positioned between upper plates 60 and shells 70 toform an upper cavity 80 into which the molten thermoplastic injectionmaterial is injected in conventional manner by the injection moldingmachine 50. As is the case for the conventional injection moldingprocess, the upper mold 55 includes two shells 70 and two plates 60which, when closed, provide the upper cavity 80 into which heated,molten injection material is injected under pressure. The mold 55 alsoincludes a channel (not illustrated) extending from an opening to thecavity 80 for passage of the pressure-injected injection material intothe cavity 80 to completely fill it, whereby the thermoplastic materialadheres to the sock lining 20.

For the illustrated embodiment, the sole 140 of the footwear product isalso injection molded by the injection molding machine 50 during thesame injection cycle. The sole mold 115 includes a shell 100 and twoplates 105, 110 as shown in FIG. 2. To provide processing efficiency,the illustrated exemplary injection molding machine 50 includes two solemold shells 100 which are both attached to a rotatable plate 105. Aftereach injection cycle of the injection molding machine 50 the plate 105is rotated 180 degrees whereby an empty shell 100 is positioned oppositea cover plate 110 attached to a table 90 of the injection moldingmachine and the other shell 100, for which a sole injection has justbeen completed, is moved away from the cover plate 110 and in-line withthe upper mold 70. This enables the injection molding machine 50 to moldboth a boot upper 130 and a boot sole 140 during one injection cycle andattach to a boot upper 130 molded during the same injection cycle a bootsole 140 that was molded during the previous cycle. Since the liquidinjection material would flow between sole and upper if both were to bemolded and attached at the same time, a previously molded sole isattached to an upper during the molding of the upper, and another soleis molded at the same time so it is ready for attachment to thenext-molded upper.

With reference to FIG. 2, when the upper plates 60 are closed the soleshell 100 opposite the cover plate 110 is tightly closed onto the coverplate 110 to form a cavity (not illustrated) between them into which aninjection material for the sole is injected during the same injectioncycle that the upper cavity 80 is injected with the injection materialfor the upper. At the same time, the other sole shell 100, which isfilled with a molded sole made during the previous injection cycle, istightly closed onto the end of the upper mold 55 in-line with the bottomof the sock lining 20. That previously made molded sole attaches to theupper while the upper is molded.

After injection of the thermoplastic material into the upper cavity 80and sole cavity formed between the sole shell 100 and cover plate 110,it is cooled and hardens, thereby forming the molded boot. Whensufficiently cooled, the plates 60, 105, 110 of the molds are opened(separated) and an operator of the injection molding machine 50 removesthe finished waterproof boot having an attached lining 120 from the last10 while the last holder 40 remains attached to the upper mold 55.

The upper mold 55 is designed to provide full coverage of the injectionmaterial into the cavity 80. To do so, the design is crafted to takeinto consideration the non-uniform reaction of the microcellularmaterial of the sock lining 20 as and when it is exposed to highpressure, high temperature and high stress during the injection moldingprocess. For example, the exemplary 3 mm thick sock lining 20 willcompress 0.075 mm more at the edges, where the mold closes, than in themiddle of the mold. The surfaces of the shells 70 are designed toaccount for the dynamic compression changes which the sock lining 20will undergo during the injection molding process, by allowing more (orless) space to form for the cavity 80 in relation to the compressionfactor of the sock lining 20 at the adjacent surfaces of the shells 70.

Injection ports of the mold (not illustrated) are provided for thepassage of the molten injection material from an injector (notillustrated) of the injection molding machine 50. For the illustratedembodiment, the injection ports are unconventionally placed on theoutside of an upper shell 70, rather than being hidden on the sole mold115 as in the conventional injection molding process, to allow for abetter flow of the injection material and filling of the upper moldcavity 80. If, instead, the upper mold 55 is injected in conventionalmanner, the top of the toe area of the boot will have a joint line and,depending upon the application, this may not be desirable for aestheticreasons. It may also decrease durability because a joint line may bemore prone to crack when the boot is worn.

As for conventional molds, the particular positioning and configuration(i.e. size and shape) to be selected for the injection ports alsoaffects the timing of the contact of the injection material with thesock lining. If there is insufficient spacing for the injection materialto flow and reach the extremities of the cavity, within seconds at thevery high pressures and temperatures applied by the injection moldingprocess, the injection material will become obstructed and the delay inflow will cause it to harden too early, not fill the cavity and clog theinjector of the injection molding machine. Also, the upper mold 55 isdesigned so as to produce no overspill of the injection material whichoccurs when the edges of the mold plates are not sufficiently sealedtogether after the mold is closed.

The details of the illustrated embodiment may be varied as consideredexpedient to a person skilled in the art and are not to be consideredessential to the invention by reason only of inclusion in the preferredembodiment. Rather, the invention is defined by the appended claims.

1-20. (canceled)
 21. A method for making an injection molded waterproofboot comprising a molded upper portion and a compressible liningmaterial attached thereto whereby the compressible lining materialbecomes attached to the molded upper portion during injection molding ofthe upper portion, the method comprising: (a) providing a last having anexterior surface which corresponds to an interior surface of the boot;(b) covering at least a portion of the exterior surface of the last witha compressible microcellular lining material which compresses underpressure, the lining material having a foot portion adapted to cover awearer's foot, and a leg portion adapted to extend up a part of thewearer's leg, with a widened area for receiving the wearer's calf; (c)providing an upper mold configured for injection of a flowable injectionmaterial into an injection cavity to form the upper portion wherein theupper mold comprises first and second shells, each said shell having apre-determined configuration, wherein the upper mold is designed to formthe molded upper portion in a desired shape such that, in the boot, themolded upper portion has a molded foot portion adapted to extendcompletely around the wearer's foot and to cover the foot portion of thelining, and an upwardly-extending molded portion adapted to extendupward from the molded foot portion and to cover a part of the legportion of the lining while leaving another part of the leg portion ofthe lining uncovered; and the pre-determined configuration of each saidshell is designed to account for a dynamic non-uniform compression ofthe lining material during the injection molding, the pre-determinedconfiguration of the shells designed to form: (i) prior to the injectionmolding, a pre-injection cavity between the shells and the liningmaterial covered last when the lining material covered last is locatedin the mold between the first and second shells, and with the shells ina closed position for injection molding; and (ii) when the liningmaterial covered last is located in the mold with the shells in a closedposition and the injection material is being injected, a dynamicallyformed injection cavity between the shells and the lining materialcovered last wherein the configuration of the injection cavity isdynamically formed by pressure applied during the injection of theinjection material which causes the lining material to compress andthereby reconfigure the pre-injection cavity to form the injectioncavity; (d) locating the lining material covered last between the firstand second shells, closing the first and second shells in position forinjection molding, the pre-injection cavity formed between the shellsand the lining material covered last, and closing a sole shellcontaining a boot sole onto the ends of the first and second shells inline with the bottom of the lining material; (e) injecting the flowableinjection material into the pre-injection cavity between the shells andthe lining material covered last to form and fill the injection cavitywith injection material; (f) hardening the injected injection material,whereby the hardened injection material attaches to the lining materialand the boot sole, the hardened injection material forming the moldedupper portion, wherein the molded upper portion, the attached liningmaterial, and the attached boot sole together form the boot; (g) openingthe mold to expose the boot; and (h) removing the boot from the last.22. The method according to claim 21 wherein the boot is a winter boot.23. The method according to claim 21 wherein the boot is a rain boot.24. The method according to claim 21 wherein the step of injecting theflowable injection material comprises injecting the flowable injectionmaterial through an injection port on the upper mold.
 25. The methodaccording to claim 21 wherein the step of injecting the flowableinjection material comprises injecting the flowable injection materialthrough an injection port on the upper mold and not through the soleshell.
 26. The method according to claim 21 wherein the step ofinjecting the flowable injection material consists of injecting theflowable injection material through the upper mold.
 27. A method formaking an injection molded waterproof boot comprising a molded upperportion and a compressible lining material attached thereto whereby thecompressible lining material becomes attached to the molded upperportion during injection molding of the upper portion, the methodcomprising: (a) providing a last having an exterior surface whichcorresponds to an interior surface of the boot; (b) covering at least aportion of the exterior surface of the last with a compressiblemicrocellular lining material which compresses under pressure, thelining material having a foot portion adapted to cover a wearer's foot,and a leg portion adapted to extend up a part of the wearer's leg, witha widened area for receiving the wearer's calf; (c) providing an uppermold configured for injection of a flowable injection material into aninjection cavity to form the upper portion wherein the upper moldcomprises first and second shells, each said shell having apre-determined configuration, wherein the upper mold is designed to formthe molded upper portion in a desired shape such that, in the boot, themolded upper portion has a molded foot portion adapted to extendcompletely around the wearer's foot and to cover the foot portion of thelining, and an upwardly-extending molded portion adapted to extendupward from the molded foot portion and to cover a part of the legportion of the lining while leaving another part of the leg portion ofthe lining uncovered; (d) locating the lining material covered lastbetween the first and second shells, closing the first and second shellsin position for injection molding, and closing a sole shell containing aboot sole onto the ends of the first and second shells in line with thebottom of the lining material; (e) injecting the flowable injectionmaterial between the shells and the lining material covered last to fillthe injection cavity with injection material; (f) hardening the injectedinjection material, whereby the hardened injection material attaches tothe lining material and the boot sole, the hardened injection materialforming the molded upper portion, wherein the molded upper portion, theattached lining material, and the attached boot sole together form theboot; (g) opening the mold to expose the boot; and (h) removing the bootfrom the last.
 28. The method according to claim 27 wherein the boot isa winter boot.
 29. The method according to claim 27 wherein the boot isa rain boot.
 30. The method according to claim 27 wherein the step ofinjecting the flowable injection material comprises injecting theflowable injection material through an injection port on the upper mold.31. The method according to claim 27 wherein the step of injecting theflowable injection material comprises injecting the flowable injectionmaterial through an injection port on the upper mold and not through thesole shell.
 32. The method according to claim 27 wherein the step ofinjecting the flowable injection material consists of injecting theflowable injection material through the upper mold.